Dosing pump

ABSTRACT

A dosing pump is provided comprising a working membrane defining a working area, and a pump drive for creating an oscillating movement of the working membrane. The direction of the pump drive can be inverted and the displacement element can be moved back and forth. The inventive dosing pump also comprises a position sensor for detecting the position of the pump drive, an electronic control system for the same, and a pump head in which an inlet valve and an outlet valve are arranged. The pump drive comprises a positioning motor and can be displaced back and forth in an oscillating manner, with the part thereof connected to the displacement element, in any range of its entire working displacement, according to a pre-determinable course, for a reduced pump capacity in relation to the maximum pump capacity. At least the inlet valve is externally controlled and comprises a motor-driven valve drive. The electronic control system is connected to at least the motor-driven valve drive(s) of the inlet and/or outlet valves, to the positioning motor of the pump drive, and to the position sensor for detecting the position of the displacement element and/or the pump drive. The combination of the electronically controllable positioning motor, the oscillating movement of the pump drive within any range of its entire working range, and the use of an externally controlled inlet and/or outlet valve significantly enlarges the operative range of the inventive dosing pump.

BACKGROUND

[0001] The invention relates to a dosing pump, particularly a diaphragm dosing pump comprising a working membrane or a similar displacement element defining a working area and a pump drive for creating an oscillating movement of the displacement element. The direction of the pump drive can be reversed and the displacement element can be moved back and forth. The invention also comprises a position sensor for detecting the position of the pump drive and an electronic control system for the drive, as well as a pump head, in which an inlet valve and an outlet valve are arranged.

[0002] Dosing pumps of this type are known in various configurations. There are known dosing pumps, which operate by a magnetic drive and execute fast working strokes. This pulse-like feeding produces sufficient pressure differences for the control of the valves.

[0003] For dosing pumps, in which a small feeding rate and small doses are desired, motor-driven rotary drives which run very slowly, at least in the dosing stroke, are used. Corresponding by, small pressure differences appear, so that sealing problems can occur for the valves.

[0004] From EP 0 321 339, a device for regulating the pump capacity of a dosing pump is known, with which the feeding stroke or the number of feeding strokes per unit of time can be changed.

[0005] The feeding stroke is changed by moving the pump drive forwards and backwards for different rotational segments with corresponding different strokes, starting from a defined home position.

[0006] In such dosing pump, sealing problems also occur at the valves for adjustable, small doses, thereby considerably reducing the desired dosing accuracy of the pump.

[0007] From DE 195 25 557.7, a diaphragm dosing pump is known, whereby special valves are used in order to avoid, at least for the most part, the previously mentioned disadvantages for a low working rate and small pressure differences, as well as small dosing amounts. However, here a minimal pressure difference is necessary for opening and closing the valves.

[0008] However, for dosings where the working stroke is drawn over a long period of time, e.g., a few minutes, a reliable seal can also not be achieved with these fine acting valves.

[0009] Furthermore, dosing pumps are known, wherein a mechanical change of the stroke length is performed to adjust the dosing amount. Therefore, small dosing amounts having a sufficiently high feeding rate, which produces a sufficient pressure difference and is sufficient for the functioning of the valves, can also be processed. However, the pumping medium is discharged at a high speed corresponding to the working rate sufficient for the functioning of the valves. This pulse-like feeding is undesirable in many dosing pumps applications.

[0010] Both slow and fast-running pumps produce conflicts between the valve functions, which have disadvantageous effects on, among other things, the pressure and suction side pressure relationships in the form of a reverse flow of pumping medium against the feeding direction thus producing dosing inaccuracies.

SUMMARY

[0011] The object of the present invention is to create a dosing pump, which can cover a broad operating range with very small dosing amounts and high repeatability, and which can provide exact adjustability of the pump over a wide range of operating conditions, wherein the pump shall exhibit high dosing accuracy both for large and also for very small feeding amounts and wherein the feeding rate can also be set to an extremely low value while maintaining high dosing accuracy.

[0012] To achieve this object, it is proposed that the pump drive has a reciprocating positioning motor with a part connected to a displacement element that can move back and forth in any range of its total working movement with a predetermined stroke for a feeding amount that is reduced relative to the maximum feeding amount. The pump further comprising two or more valves whereby at least one is remote controlled and has a motor-driven valve drive. An electronic control system is connected at least to the motor-driven valve drive or drives of an inlet and/or outlet valve, to a pump drive, and also to a position sensor for detecting the position of the displacement element and/or the pump drive.

[0013] The combination of an electronically controllable positioning motor, a reciprocating movement of the pump drive within any range of its total working area, and also the use of a remote-controlled inlet and/or outlet valve enables a considerably expanded usable range of a dosing pump equipped with these devices.

[0014] Thus, there is the possibility of allowing the dosing pump to operate for very small dosing amounts at an extremely low feeding rate and to achieve an exact dosing through the valve or valves, which can be precisely controlled by the electronic control system and thus opened or closed at predetermined times independent of feeding pressure differences.

[0015] Alternatively, in a higher pump capacity and fast-running pump drive, a reverse flow can be prevented due to counter pressure of the pumping medium by means of matching closing and opening times by the remote-controlled valve. This also contributes to an improvement in the dosing accuracy and universal application of the dosing pump.

[0016] Finally, in addition to an adapted control of the positioning motor by the electronic control system, through the reciprocating stroke movement in any range of the total working movement for a rotary pump drive, the reciprocating stroke can be influenced as a function of the position within the total working area.

[0017] Thus, by selecting the position of the oscillating stroke movement according to the task, within a 360° total working area, the effective stroke of the displacement element can be influenced. For an oscillating stroke movement in the area of a dead center position of a pump drive with a crank mechanism, for a given rotational movement, a smaller effective stroke is produced than in an area between these two dead center positions.

[0018] The dosing pump according to the invention can be operated both in any range of the total working movement of its pump drive with an oscillating working stroke moving back and forth and also rotating with maximum working stroke and corresponding maximum feeding amount per working stroke. This produces a wide range of uses for the dosing pump.

[0019] The electronic control system can be configured for variable control of the motor-driven valve drive or drives of the inlet and/or outlet valve as a function of the position of the displacement element. Furthermore, the electronic control system may control the motor-driven valve drive or drives of the inlet and/or outlet valve as a function of different operating parameters, especially as a function of operating pressure, revolutions per minute (rpm), consistency of the pumping medium, and the like.

[0020] For example, the switching positions of the valve or valves within a rotating or an oscillating stroke area are chosen as a function of the operating pressure, such that pump capacity loss due to counter pressure is minimized. The matching switching positions can be determined through tests, furthermore, there is also the possibility of performing a variable correction of the switching positions as a function of operating pressure, if this is changed. The corresponding default settings can be set manually or by analog or digital means.

[0021] The electronic control system can have a memory means for storing various operating parameters and for assigning these operating parameters to different control times of the valve or valves. The operating parameters stored in the memory means can be selected either manually or selected by measuring the actual operating parameters and assigning the stored operating parameters.

[0022] For the latter case, corresponding measurement devices for measuring, e.g., operating pressure, counter pressure, rpm, and the like are provided.

[0023] In a preferred embodiment that has been reduced to practice, the pump drive can have a cam or crank drive with a rotating crank element and a connecting rod connected to the working membrane or a similar displacement element, wherein the crank element can be moved back and forth in an oscillating movement in any range within the total rotational movement for small deflections of the working membrane relative to the maximum possible deflections for a rotational movement. The cam or crank drive converts a rotating movement into a linear movement of the displacement element. This executes back and forth movements within the extreme positions in the upper and lower dead centers of the crank drive. In contrast, the oscillating stroke movement provides a small working stroke and has a significantly smaller amplitude, wherein the drive does not rotate, but instead moves back and forth correspondingly within the possible rotation of its rotating crank element by controlling the driving positioning motor correspondingly.

[0024] Here, the reciprocating stroke movement with reduced amplitude relative to the maximum amplitude, both the number of working strokes of the working membrane, or the like, per unit of time and/or the drive speed can be adjusted. The dosing amounts can be influenced by both measures and also the pump characteristics, particularly with regard to the feeding rate. Thus, for a constant feeding amount, a smaller stroke at a higher working speed or the inverse, a larger stroke at a lower working speed, can be set. In the latter case, the pumping medium is fed more gently.

[0025] Furthermore, the electronic control system may be set to a non-constant drive speed of the drive motor, particularly for a fast suction stroke and a correspondingly slower dosing stroke. Thus, an irregular or pulse-like discharge of the pumping medium can be reduced. This compensation corresponds approximately to a sinusoidal movement with the overlapping of hydraulic phenomena unique to diaphragm pumps. The matching stroke compensation can be preset by a speed profile per rotation or working stroke, which is stored as parameters in the electronic control system.

[0026] According to one embodiment of the invention, the inlet and/or outlet valve can have an electromagnetic stroke magnet as a motor-driven valve drive. The electromagnetic stroke magnet has a stroke armature that is guided by means of leaf springs set at a distance from each other and that is in drive connection with a valve closing body. The support of the armature of the stroke magnet with the help of at least two leaf springs produces a spring parallelogram suspension, which is practically free from wear and tear and insensitive to contamination, because there are no parts supported by sliding guides. Simultaneously, the armature is precisely guided in the radial direction and play-free in the stroke direction. The stroke drive for the inlet valve and/or for the outlet valve has an especially long service life due to these means.

[0027] Advantageously, at least one of the leaf springs of the stroke armature guide is pre-tensioned in the closing direction of the remote-controlled valve. The valve is therefore closed for an inactive stroke and thus sealed tightly against reverse flow. In addition, a cost-effective, simple-acting stroke electromagnet can be used, because the leaf spring(s) can assume the closing movement of the valve.

[0028] According to one configuration of the invention, instead of a remote-controlled valve, at least one valve particularly with an elastic valve disk, that can be activated by the pumping medium. The elastic valve disk contacts, in the closing position with a flat side on the opening edge of a supply channel forming a valve seat. On the side of the valve disk facing away from the supply channel there is a bridge-like support supporting the valve disk at least in the valve opening position within the extended projection of the supply channel.

[0029] The provided construction of the valve produces a good seal also for only small pressure differences possibly occurring during operation. Therefore, the pump has good vacuum properties even at low working speeds.

[0030] It is advantageous if the previously described valve that can be activated by the pumping medium forms a complete, exchangeable unit and is formed as a valve insert with a support plate having the support and a discharge channel, a valve holding plate, and also the valve disk, and that preferably the support plate and the valve holding plate have edge formations that engage each other and are especially welded, adhered, or similarly connected to each other in the assembled position.

[0031] Therefore, the parts for the complete valve inserts can be manufactured independently of the pump head, in which the valve insert is inserted, which has considerable advantages in terms of accuracy for molding technology.

[0032] The high precision of valve parts leads to, among other things, a tension-free support of the valve disk, which is a prerequisite for acceptable operation of the valves with good sealing even at low pressure differences and very slow movement sequences. In addition, the valve inserts can be exchanged as a whole very simply.

[0033] The pump drive can have, as the drive and positioning motor, a controlled or a regulated motor particularly a stepper motor or a motor regulated by a control loop, e.g., a servo DC motor or the like. Thus, it is possible to travel a defined angle at a defined speed. The rotational direction of the motor is reversible, so that the correspondingly small-stroke reciprocating stroke movements can be performed within the total working movement.

[0034] A preferred position sensor is a non-contact, e.g., optoelectronic or magnetic position sensor, which interacts with the positioning motor or a part driven by this motor and is connected to the control electronics. Therefore, the position of the working membrane is known in each operating phase so that for a corresponding drive motor working in a control loop, this motor receives positioning feedback and on the other hand the inlet and/or outlet valve can be exactly adapted to the position of the working membrane. The position sensor can be configured so that it outputs a reference signal at clearly defined positions, e.g., at the top or bottom dead center, from which the intermediate positions can be calculated within a rotation or a reciprocating movement of the pump drive. However, the position sensor can also have an encoder, through which the appropriate position of the pump drive or the working membrane driven by this drive can be determined directly.

[0035] Additional configurations of the invention are listed in the other subordinate claims. The invention is described below in even more detail with its essential features with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1: a perspective representation of a dosing pump with control system,

[0037]FIG. 2: a sectional representation of a dosing pump with an electromagnetically activated inlet valve,

[0038]FIG. 3: a longitudinal sectional representation, as well as

[0039]FIG. 4: a cross-sectional representation of a dosing pump, and

[0040]FIG. 5: a cross section of a valve insert.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] A dosing pump 1 shown in FIG. 1 having a motor-driven pump drive 2 for a reciprocating movement of a displacement element. The dosing pump 1 has a pump housing 3 with a pump head 4, in which at least one inlet valve and one outlet valve are arranged. To activate these valves, electromagnetic stroke drives 5, 6 are provided in the embodiment according to FIG. 1.

[0042] The electromotor-driven pump drive 2, the electromagnetic stroke drives 5, 6 for the valves, and a position sensor for detecting the position of the pump drive are connected to an electronic control system 7. With the help of this electronic control system 7, the pump drive 2 formed can be variably controlled by a positioning motor with reference to its rpm and its rotational direction. In addition, the electronic control device 7 is formed so that the pump drive can move back and forth in an oscillating movement with the positioning motor in any range of its total working movement with a stroke that can be preset.

[0043] This reciprocating stroke movement can be used to define a feeding amount that is reduced relative to the maximum feeding amount. Thus, the pump drive can be operated with a rotational angle and a speed that can be preset.

[0044] The valves provided in the embodiment according to FIG. 1 with electromagnetic stroke drives 5 and 6 also allow closing and opening times that can be variably assigned to the working position of the pump drive. Thus, a plurality of operating parameters can be defined in order to be able to adapt the pumps to the widest range of operating conditions.

[0045] In a sectional representation, FIG. 2 shows the inner structure of a dosing pump according to the invention. This depicts a diaphragm pump with a membrane 8 as the displacement element, wherein the membrane has a crank drive 9 with a rotating crank element 10 and a connecting rod 11 connected to the membrane 8 as the pump drive. The crank element 10 is connected to positioning motor 12 (refer to FIG. 3).

[0046] In the embodiment shown in FIG. 2, only the inlet valve 13 is provided with an electromagnetic stroke drive 5, while the outlet valve is a valve that can be activated by the pumping medium.

[0047] Here, the outlet valve 14 is formed as a valve that is sensitive to small pressure differences. For certain dosing tasks, which operate with a minimum feeding rate, this configuration provides good use with different valves.

[0048] However, if the feeding rate falls below this minimum value necessary for a valve activated by the pumping medium, or if special dosing tasks are to be preformed, remote-controlled valves are provided both for the inlet valve and also for the outlet valve. Therefore, the closing and opening of the valves can be performed independent of the pressure difference appearing in the valve area. Thus, the valve function can also be decoupled from the corresponding position of the pump drive.

[0049] For the use of a valve activated by the pumping medium, as provided in the embodiment according to FIG. 2, valve 15 shown in FIG. 5 can be provided selectively as an inlet valve or outlet valve. This valve 15 for example, is configured so that it exhibits a reliable sealing behavior even for low working or feeding rates and the resulting low pressure differences between the suction side and the pressure side.

[0050] The valve is formed as a disk valve and essentially has a support plate 16, a valve disk 17, and also a valve holding plate 18. A complete, can-shaped unit as the valve insert is formed by these three parts 16, 17, and 18. This valve insert can be inserted into a corresponding holding recess of the pump head.

[0051] For a valve arranged on the suction side, in the closed position the valve disk 17 lies with its flat side facing the suction side 19 on the opening edge 20 of a central supply channel 21 forming a valve seat in the valve holding plate 18. The valve disk 17 is fixed against lateral displacements by positioning tabs, which are arranged laterally adjacent to the opening edge and engage in open recesses in the edge of the valve disk 17. The support plate 16 has a bridge-like support 22 within the extended projection of the supply channel of the valve holding plate 18, by means of which the valve disk 17 is supported in the opening position approximately along its diameter. In the open position of the valve, the valve disk tabs located on both sides of the center support line are pivoted towards the support plate 16, so that the supply channel 21 is opened. The distance of the plane running through the support point of the support 22 from the parallel plane formed by the opening edge 20 is dimensioned so that the valve disk 17 is held there tension-free. This is a prerequisite for the valve disk to respond at very low pressure differences and also for a fast closing or opening process.

[0052] For the use of the valve 15 on the pressure side, the valve is inserted turned by 180 degrees.

[0053] As previously mentioned, remote-controlled valves are preferably used both for the inlet valve 13 and also for the outlet valve 14. One such valve is shown as an inlet valve in FIG. 2. The electromagnetic stroke drive 5 has a stroke armature 25, which is guided by means of leaf springs 23, 24 spaced apart from each other and which is in drive connection with a valve closing body 26.

[0054] In the axial extension of the stroke armature 25, a sleeve-like iron pole 27 is arranged at a distance to the armature. Around this pole and the stroke armature there is located a coil 28, which, when it is excited, moves the stroke armature 25 in the direction of the arrow Pf 1 and thus brings the valve closing body 26 into the open position.

[0055] A parallelogram suspension for the stroke armature 25 is formed by the two leaf springs 23, 24, so that no parts supported by sliding guides are necessary. Thus, the stroke armature 25 is guided in the radial direction precisely and play-free in the stroke direction. Preferably, at least one of the two leaf springs of the stroke armature guide is pretensioned in the closing direction. Therefore, in the no-current state the valve goes into the closed position, which is shown in FIG. 2.

[0056] To transfer the stroke movement of the stroke armature 25 to the valve closing body 26, there is a rocker lever 29, which is coupled with its drive end to a shaft 30 connected to the stroke armature and with its other end is connected to the valve closing body 26. In the course of the longitudinal extension of the rocker lever 29, there is a rocker support 31, which encloses the rocker lever 29 in a sealing manner and which also seals a valve space from the outside.

[0057] The rocker support is preferably formed as an elastomer bushing, so that an absolute seal is provided.

[0058] The dosing pump 1 is equipped with a position sensor 32 for detecting the position of the pump drive or the membrane 8 forming the displacement element, as can be easily seen in FIGS. 3 and 4. In this embodiment, the position sensor has a magnet 33 rotating with the crank element 10, as well as a magnetic sensor preferably formed as a Hall sensor and arranged stationary adjacent to the rotational track of the magnet 33. Thus, for each rotation of the pump drive, a reference signal is generated. The other positioning device is oriented accordingly to this reference signal. Particularly for the use of a stepper motor, for which the corresponding positioning can be set by a certain number of steps, the reference signal is used for resetting or for generating a certain correction value. With the use of a stepper motor, very small step angles are possible, so that the membrane 8 can be brought into any arbitrary position within its total working area. Thus, the setting can proceed extremely slowly, wherein working strokes extending over several minutes are possible. However, on the other hand, higher RPMs can also be processed in order to achieve a high pump capacity.

[0059] In addition to the non-contact position sensor shown in the embodiment, other sensors e.g., optoelectronic, position, can also be used, which output a plurality of position data, if necessary, over the course of one rotation. Here, it should be mentioned that instead of a stepper motor, a motor working in a control loop, e.g., a servo DC motor, can also be used.

[0060] As can be seen in FIG. 1, the positioning motor 2, the electromagnetic stroke drives 5 and 6 for the inlet valve 13 and the outlet valve 14, and also the position sensor 32 are connected to the electronic control system 7. Therefore, the function of the pump can be varied within wide limits. For example, the electro-magnetic stroke drives 5, 6 of the valves can be controlled as a function of the position of the membrane 8.

[0061] However, on the other hand there is also the possibility to open or close the valves independent of the position of the pump drive or the membrane. For example, this can occur as a function of different operating parameters, especially as a function of operating pressure, rpm, consistency of the pumping medium, and the like. By the use of a memory device, there it is possible to store different operating parameters which can then be assigned to different control times of the valves.

[0062] For measuring operating parameters, such as, e.g., operating pressure, counter pressure, rpm, corresponding measurement devices are provided.

[0063] In addition to the function of the pump, mentioned above, with a membrane that can move back and forth in an oscillating movement within the total working movement for a reduced feeding amount, a non-uniform working rate of the drive motor can also be set with the help of the electronic control system 7 for a fast suction stroke and a correspondingly slower dosing stroke. Therefore, instead of an otherwise approximately sinusoidal fluid feeding, the flow can be made more uniform.

[0064] If both valves are remote-controlled, then there is also the possibility of controlling the feeding device. Even for a dosing pump, this possibility is an advantage, because after a dosing process with discharge of the pumping medium from the pressure channel, undesired reverse flow or return drops of the pumping medium can be prevented by switching the feeding direction through the control of both valves. To prevent the previously mentioned reverse flow or return droplets of pumping medium, a partial stroke of the working membrane with a controlled valve closing is usually sufficient.

[0065] This means that for the suction stroke of the membrane with enlargement of the working space, the outlet valve is opened while the inlet valve is closed.

[0066] The dosing accuracy of the dosing pump 1 can be significantly improved by these measures and simpler handling is also possible when setting the dosing amount.

[0067] The dosing pump 1 with remote-controlled inlet and outlet valve 13, 14 can be used not only for reverse feeding for preventing reverse flow, but also selectively for continuous feeding in both feeding directions. 

1. A diaphragm dosing pump comprising a working membrane or a similar displacement element defining a working area and a pump drive (2) for creating an oscillating movement of the displacement element, whereby the pump drive (2) can be reversed in direction and the displacement element can be moved back and forth, whereby a position sensor for detecting a position of the pump drive (2) and an electronic control system (7) for the pump drive are also provided, as well as a pump head, in which an inlet valve and an outlet valve (14) are arranged, the pump drive (2) has a positioning motor and can move back and forth in an oscillating movement, by a part connected to the displacement element, in any range of a total working movement by a stroke that can be preset for a feeding amount that is reduced relative to a maximum feeding amount, at least one of the valves (13) is remote controlled and has a motor-driven valve drive, and the electronic control system (7) is connected to the motor-driven valve drive of the inlet and/or outlet drive (14), to the positioning motor of the pump drive (2), and also to a position sensor for detecting a position of the displacement element and/or the pump drive (2).
 2. A dosing pump (1) according to claim 1, wherein the pump drive (2) is configured and controlled by a part connected to the displacement element for a feeding amount per working stroke that is increased or at a maximum relative to a reduced feeding amount by a working stroke that can be moved back and forth in an oscillating movement.
 3. A dosing pump (1) according to claim 1, wherein the electronic control system (7) is configured for variable control of the motor-driven valve drive of the inlet (13) and/or outlet valve (14) as a function of the position of the displacement element.
 4. A dosing pump (1) according to claim 1, wherein the electronic control system (7) is configured for controlling the motor-driven valve drive(s) of the inlet (13) and/or outlet valve (14) as a function of different operating parameters, comprising at least one of a function of operating pressure, rpm, and consistency of the pumping medium.
 5. A dosing pump (1) according to claim 1, wherein the electronic control system (7) has a memory device for storing different operating parameters and for assigning these operating parameters to different control times of the valves.
 6. A dosing pump (1) according to claim 1, wherein one or more measurement devices for measuring operating parameters, comprising at least one of operating pressure, counter pressure, rpm, and pump capacity are provided.
 7. A dosing pump (1) according to claim 1, wherein the pump drive (2) has a cam or crank drive (9) with a rotating crank element (10) and a connecting rod (11) connected to the working membrane or a similar displacement element and the crank element (10) for small deflections of the working membrane relative to the maximum possible deflections for one rotation movement can move back and forth in an oscillating movement in any range within a total rotational movement.
 8. A dosing pump (1) according to claim 1, wherein the electrically remote-controlled valve (15) is closed in an inactive state.
 9. A dosing pump (1) according to claim 1, wherein the inlet and/or outlet valve (13, 14) has as a motor-driven valve drive an electromagnet stroke magnet (5, 6), which has a stroke armature (25) guided by leaf springs (23, 24) spaced apart from each other, which is in drive connection to a valve closing body (26).
 10. A dosing pump (1) according to claim 9, wherein at least one of the leaf springs (23, 24) of the stroke armature guide is pre-tensioned in the closing direction of the remote-controlled valve (15).
 11. A dosing pump (1) according to claim 1, wherein in addition to a remote controlled valve, there is at least one valve (15) that can be activated by the pumping medium, especially formed with an elastic valve disk (17), which in the closed position contacts with a flat side onto the opening edge (20) of a supply channel (21) forming a valve seat, and on the side of the valve disk facing away from the supply channel (21), a bridge-like support (22) supports the valve disk (17) at least in an the opened position within the extended projection of the supply channel (21).
 12. A dosing pump (1) according to claim 11, wherein the valve (15) that can be activated by the pumping medium forms a complete, exchangeable unit and is configured as a valve insert (21) with a support plate (16) having support (28) and a discharge channel (31), a valve holding plate (18), the valve disk (17), support plate (16) and the valve holding plate (18) preferably have edge formations that engage with each other and are welded, adhered, or connected to each other in the assembled position.
 13. A dosing pump (1) according to claim 1, wherein the output position of the working membrane (6) is the same at the beginning and end of a dosing.
 14. A dosing pump (1) according to claim 1, wherein a number of working strokes of the working membrane (6) per unit of time and/or the working rate can be adjusted.
 15. A dosing pump (1) according to claim 1, wherein the pump drive (2) has as a drive and positioning motor (12) a controlled or regulated motor, particularly a stepper motor or a motor working in a control loop.
 16. A dosing pump (1) according to claim 1, wherein a non-contact optoelectronic or magnetic position sensor (32) is provided as the position sensor (32), which interacts with the positioning motor (12) or a part driven by this motor and is connected to the control electronics (7).
 17. A dosing pump (1) according to claim 1, wherein the electronic control system (7) is configured for setting a non-uniform drive rate of the drive.
 18. A dosing pump according to claim 1, wherein the two valves are remote-controlled and can be controlled selectively as an inlet valve or outlet valve for reversing a feeding direction. 